Lithium ion capacitor

Abstract

A lithium ion capacitor includes a positive electrode, a negative electrode, and a non-protonic organic solvent electrolytic solution of a lithium salt. A positive electrode active material is a material capable of reversibly doping a lithium ion and/or an anion. A negative electrode active material is a material capable of reversibly doping a lithium ion. The lithium ion is doped in advance to either one or both of the negative electrode and the positive electrode so that a positive electrode potential after the positive electrode and the negative electrode are short-circuited is 2.0 V (relative to Li/Li + ) or less when capacitance per unit weight of the positive electrode is C + (F/g), weight of the positive electrode active material is W + (g), capacitance per unit weight of negative electrode is C − (F/g), and weight of the negative electrode active material is W − (g), a value of (C − ×W − )/(C + ×W + ) is 5 or more.

1. A lithium ion capacitor comprising:
 a positive electrode, a negative electrode, and a non-protonic organic solvent electrolytic solution of a lithium salt as an electrolytic solution, 
 wherein a positive electrode active material is a material capable of reversibly doping a lithium ion and/or an anion; 
 a negative electrode active material is a material capable of reversibly doping a lithium ion; 
 the lithium ion is doped in advance to either one or both of the negative electrode and the positive electrode so that a positive electrode potential after the positive electrode and the negative electrode are short-circuited is 2.0 V (relative to Li/Li + ) or less; 
 when capacitance per unit weight of the positive electrode is C + (F/g), weight of the positive electrode active material is W + (g), capacitance per unit weight of negative electrode is C − (F/g), and weight of the negative electrode active material is W − (g), a value of (C − ×W − )/(C + ×W + ) is 6.8 or more and 22.8 or less; and 
 the weight of the positive electrode active material is larger than the weight of the negative electrode active material. 
 
     
     
       2. The lithium ion capacitor according to  claim 1 , wherein either one or both of the positive electrode and the negative electrode, respectively, are provided with a current collector having a hole penetrating through front and back surfaces thereof; and
 the lithium ion is doped to the negative electrode through an electrochemical contact of the negative electrode and a lithium ion supply source. 
 
     
     
       3. The lithium ion capacitor according to  claim 2 , wherein the negative electrode active material has capacitance per unit weight three-times or more that of the positive electrode active material. 
     
     
       4. The lithium ion capacitor according to  claim 1 , wherein the negative electrode active material has capacitance per unit weight three-times or more that of the positive electrode active material.